Vent cap



Sept- 13, 1955 E. L. GRENZEBACH ET AL. 2,717,547

VENT CAP 2 Sheets-Sheet 1 Filed Jan. 12, 1952 506/7? 15: 6AE/VZE5/4CH,

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Sept. 13, 1955 E, GRENZEBACH ET AL 2,717,547

VENT CAP Filed Jan. 12, 1952 2 Sheets-Sheet 2 064? A 5: Gauze-54c,

19 HHERY 6. Mae/(4,

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United States Patent VENT CAP Edgar Lee Grenzebach, Temple City, and Harry G. Merkel, Beverly Hills, Calif.; said Merkei assignor to said Grenzebach Application January 12, 1952, Serial No. 266,136

5 Claims. (Cl. 9866) This invention relates to ventilators and is particularly directed to improvements in vent caps of the type used for exhausting fumes, foul air, or the like from buildings, ships or other structures. Vent caps of this type are commonly employed on the roof of a building for exhausting fumes from space heaters.

It is important that vent caps of this type be capable of raising fumes and foul air through the stack at all times, regardless of the direction or velocity of the wind which strikes the exposed vent cap located on the roof of the building or in an exposed location aboard ship. Commercially available vent caps perform satisfactorily when the direction of the wind is horizontal or substantially horizontal but often give unsatisfactory results and even produce down drafts in the stack when the wind over a building is turbulent or when sharp localized up currents or down currents occur in the vicinity of the vent cap. Vent caps are commonly mounted in a vertical position adjacent an inclined roof and tests have shown that wind currents deflected from the roof may have vertical components of important magnitudes. Under such conditions down drafts may be caused in the stack.

It is accordingly an object of our invention to provide a ventilator or vent cap for a stack which will give good results regardless of the direction of the wind and regardless of localized air currents having vertical components of major proportions. We have found that by designing the inner and outer vanes or louvers to take advantage of the low pressure area down wind from the vent cap structure that the suction provided by this low pressure area can be used exclusively to create and maintain an up draft in the stack, without utilizing the positive pressure on the side of the vent cap structure against which the wind impinges. Our construction and mounting of the inner and outer louvers causes the air currents to pass around the vent cap structure and also through the passage area between the inner and outer vanes on the upstream side of the vent cap structure, but does not permit air currents to flow into the interior of the stack. On the downstream side the suction of the low pressure causes flow to occur from the interior of the stack outward through the inner and outer louvers into the low pressure area.

Another object of our invention is to provide a louver design having the characteristics outlined above but which utilizes a plurality of duplicate inner louvers and a plurality of duplicate outer louvers. Furthermore, the shape of the particular louvers is such that vent caps of different sizes can be constructed using the same identical louvers. For example, a 4" cap and a 6" cap have louvers of identical transverse dimensions, the 6" cap simply having a larger number of inner louvers and a corresponding larger number of outer louvers. This interchangeability of louvers for both the 4" and 6" standard size vent caps ofiers manufacturing economies, including a reduction in the number of dies, jigs and fixtures required and also a reduction in the required inventory of parts.

This interchangeability of inner and outer louvers for different size vent caps can be employed to great advantage when the vent caps do not differ widely in size. It has been found, however, that when the vent cap sizes vary considerably, for example 4" and 12", that the larger size cannot employ the same identical inner louvers and outer louvers used on the smaller size while preserving the required spacing and passage areas between the inner and outer series of louvers. Consequently we prefer to use the same inner louver for all sizes of vent caps and to change the transverse dimension of the outer louvers for vent caps of relatively large nominal size.

Another object of our invention is to provide a vent cap structure employing a series of inner louvers and a series of outer louvers, which structure may be readily assembled by spot welding techniques on a quantity basis for economical manufacture.

Other related objects and advantages will appear hereinafter.

in the drawings:

Figure 1 is a perspective view in diagrammatic form showing a preferred form of our invention mounted on the inclined roof of a building;

Figure 2 is a sectional elevation taken substantially on the lines 22 as shown in Figure 1;

Figure 3 is a transverse sectional view taken substantially on the lines 33 as shown in Figure 2;

Figures 4 and 5 are diagrammatic transverse sectional views showing how air currents pass through the passageways between the inner and outer louvers toward the low pressure area on the downstream side of the cap structure. Figure 4 shows the flow which occurs when the wind blows toward the space between adjacent outer louvers and Figure 5 shows how the flow occurs when the wind is directed against one of the outer louvers;

Figure 6 is a diagrammatic sectional view showing a larger size vent cap;

Figure 7 is a view similar to Figure 6, showing a still larger size of vent cap; and

Figure 8 is a perspective view, partly broken away, showing one of the outer louvers.

Referring to the drawings, the vent cap structure generally designated 10 comprises a lower annular ring or base 11 having an inner cylindrical lip 12 and a downwardly extending skirt 13. The skirt 13 is adapted to receive the upper end of the stack 14 which extends into the interior of the building 15. The stack may be connected to space heating apparatus or to any other device which may require an external vent. While we have shown the cap structure 10 mounted in an upright position, it is to be understood that in many installations the cap structure is inclined or may extend horizontally from a vertical wall, for example, when projecting into an alley between buildings, or may even be mounted upside down in extreme cases.

The structure 19 also includes an upper annular ring 16 to which is secured the conical cover 17. Inner louvers 18 and outer louvers 19 extend between the annular rings 11 and 16. The louvers may be secured to the annular rings by any convenient means, and as shown in Figure 3 of the drawings this means may comprise tabs 29 which are bent at right angles to the length of the louvers and which may be spot Welded to the rings 11 and 16. In Figure 8 the lower tabs 20 are shown after the bending operation is complete and the upper tabs 20a are shown prior to such bending operation.

In accordance with our invention, the outer louvers 19 are substantially identical and each has a relatively wide central portion 21 having a relatively large radius of curvature. The ends 22 are symmetrically placed with respect to the central portion 21 and each is formed with a reverse bend of relatively small radius of curvature.

The central portion 21 is convex on its outer surface and the end portions 22 are concave on their outer portions.

These outer louvers may be conveniently manufactured in a die long enough to receive the longest louver to be employed in a large size cap structure. Shorter louvers may be formed in the same die by inserting shorter cut lengths of strip stock into the die.

The inner louvers 18 are substantially duplicates and each has a pair of symmetrically placed curved sections 23 of relatively large radius of curvature joined by a central nose portion 24 of relatively small radius of curvature. The portions 23 are concave on their outer surfaces and the nose portion 24 is convex on its outer portion. Each of the portions 23 has a short flange 25 along each edge extending radially inwardly at an angle. They are preferably straight and are not curved. The angularity of the flanges 25 is such that the space A between curved portions 23 on adjacent louvers is less than the space B between the free ends of the flanges on such adjacent louvers. This construction insures that the entrance to the radial passages 26 between the inner louvers 13 leading into the center of the structure 10 is narrower than any other point along the length of the passages. Similarly, the inner and outer louvers are so positioned that the entrance to the ports 27 leading into the interior of the structure is narrower than the width at any other point along the length of the ports. The same is true of the entrance openings 28 between adjacent outer louvers 19 since the distance between the tip ends of the portions 22 is a minimum.

The openings and spacings between the louvers remain substantially constant regardless of the size of the vent cap structure. Vent caps of larger size employ additional louvers 0n the inner series and outer series but the spacing between louvers remains substantially constant so that the pattern of air flow is substantially the same.

When the wind is directed into the openings 28a as shown in Figure 4, the air moves into the ports 27 splitting into two streams on opposite sides of the inner louver 18a. The zone of reduced pressure on the downstream side of the vent cap structure 10 is shown by the phantom lines 29. The low pressure in this zone induces a flow of air from the center of the vent cap out through the openings 26a, 26b and 26c. The flow continues in the manner shown by the arrows so that fumes are exhausted from the cap through the openings 28b and 280 on opposite sides of the outer louver 19a. Tests show that air entering the openings 28a does not pass into the interior of the cap but on the contrary flows between the inner and outer louvers to reach the low pressure area on the the Wind is directed against one of the outer louvers instead of between the outer louvers. As shown in Figure 5, air enters the openings 28 on opposite sides of the central outer louver 19d. The air splits into two streams on opposite sides of the outer louver 19d and passes through ports 27 27g and 27/1. The air flows between the inner and outer louvers and out through the opening 28g into the zone of reduced pressure shown by the phantom lines 30. The reduced pressure in this zone induces a flow of air outward through the passages 26d on opposite sides of the centrally placed inner louver 18a.

When the Wind strikes the vent cap structure 10 at a location between the position shown in Figures 4 and 5, the passage of air through the louvers is substantially the same as that shown in Figures 4 and 5. The important point is that the stack is subjected to the reduced pressure in the zone downstream from the vent cap structure it and that the air on the upstream side of the structure 10 does not enter the central part of the cap but instead passes between the inner and outer louvers, as shown by the arrows.

iii)

One of the methods for testing efficiency of vent caps now in use is to direct a flow of air against the exterior surfaces of the vent cap structure from three diiferent directions as shown by the arrows 31, 32 and 33, in Figure 2. The tests are repeated for various positions around the periphery of the vent cap structure to determine the variation in efiiciency when the wind strikes the side of an outer louver or enters the space between outer louvers. While some forms of commercally available vent caps perform satisfactorily under test when air is caused to flow in the direction of the arrows 31, 32 and 33, it has been found that such commercial vent caps are totally unsatisfactory when the air passes at steeper angles of attack and when it passes vertically upward or vertically downward. It is known that a turbulent condition of air during storms and when passing over inclined surfaces of roofs often has substantially vertical components which may be in the nature of temporary gusts or which may last for a considerable length of time. The vent cap construction embodying our invention gives satisfactory performance without downdrafts regardless of the angle of attack of the air. It performs satisfactorily when the air moves vertically downward and also when the air moves vertically upward. It gives excellent results when the air passes in the direction of the arrow 31, 32 or 33.

The air flows through the louvers in the direction of the arrows shown in Figures 4 and 5 regardless of the angle or azimuth of attack of the wind stream. The louver design and placement is such that as the air moves into the structure between the outer louvers it is directed past a smoothly curved surface on the inner louvers. The tips of the inner louvers are formed so that the air is not directed straight across the openings between inner louvers but is directed outward through the center of the outer louvers. This is accomplished without any substantial loss in velocity. Consequently the tendency to infiltrate into the stack itself is minimized. The tendency to induce air out of the stack between two inner louvers is sufficient to overcome the suction which is built up on the downstream side. Consequently no air moves inward or outward through the opening between the inner louvers. The amount of air induced through the stack and outward on the downstream side is entirely dependent upon the negative pressure created in the zone downstream from the vent cap structure.

Figure 6 shows how the same inner and outer louvers may be employed on a larger size vent cap. The spacing between the louvers remains substantially the same but there are six inner louvers and six outer louvers instead of five each as shown in Figures 3, 4 and 5. Figure 7 shows a still larger size vent cap having seven inner louvers and seven outer louvers with the spacing of the inner and outer louvers remaining substantially the same. However, the spacing of the inner louvers is slightly greater than that shown in the other figures. This is about the maximum spacing which can be tolerated without adversely affecting the performance. For larger size vent caps, the same inner louvers may be used but the outer louvers should be altered in order that the spacing between inner louvers may not become excessive.

Having fully described our invention, it is to be understood that we do not wish to be limited to the details herein set forth but our invention is of the full scope of the appended claims.

We claim:

1. A vent cap having a circular series of vertically extending inner louvers and a circular series of vertically extending convex outer louvers, means fixing the ends of both series of louvers for maintaining them in spaced relationship, adjacent outer louvers having vertically extending curved side portions defining vertically extending openings therebetween, said curved side portions being curved outwardly of the vent cap, each inner louver in the series being positioned radially inward of one of said openings, each inner louver having a pair of curved concave portions of relatively large radius of curvature joined symmetrically by a convex nose portion of small radius of curvature, the nose portion being located centrally of said opening, each inner louver also having a pair of vertical flanges defining the side edges thereof, each flange extending radially inwardly from the end of each of said curved portions, the flanges on adjacent inner louvers defining vertically extending ports, each curved portion of each inner louver cooperating with a side portion of one of the outer louvers todefine a passage way between one of the openings and one of said ports, whereby upon subjecting the vent cap to an external air flow the air passes inward through the openings and passageways on the upstream side of the vent cap and fiows between the inner series and outer series of louvers to the openings on the downstream side of the vent cap and into the lower pressure zone caused by the external air flow, and induces a flow from the central interior part of the vent cap outward through the ports on the downstream side into said low pressure zone.

2. A vent cap comprising in combination: upper and lower supports, a circular series of vertically extending inner louvers joined at their ends to said supports, a circular series of vertically extending convex outer louvers joined at their ends to said supports, adjacent outer louvers having vertically extending curved side portions defining vertically extending openings therebetween, said curved side portions being curved outwardly of the vent cap, each inner louver being positioned radially inward of one of said openings, each inner louver having a pair of curved concave portions of relatively large radius of curvature joined symmetrically by a convex nose portion of small radius of curvature, the nose portion being located centrally of said opening, each inner louver also having a pair of flanges, one extending from the end of each of said curved portions, each of the flanges being directed radially inward at an angle, the flanges on ad jacent inner louvers defining vertically extending ports which have their narrowest dimensions between the radially outer ends of said flanges on adjacent inner louvers, each curved portion of each inner louver cooperating with a side portion of one of the outer louvers to define a passageway between one of the openings and one of said ports, the inner and outer louvers being shaped so that each of said passageways is narrower near the opening than near the port, whereby upon subjecting the vent cap to an external air flow the air passes inward through the openings and passageways on the upstream side of the vent cap and flows between the inner series and outer series of louvers to the openings on the downstream side of the vent cap and into the low pressure zone caused by the external air flow, and induces a flow from the central interior part of the vent cap outward through the ports on the downstream side into said low pressure zone.

3. A series of inner and outer louvers for use in constructing vent caps of a plurality of nominal sizes, comprising in combination: a circular series of vertically extending inner louvers and a circular series of vertically extending convex outer louvers, the outer series and the inner series having the same number of louvers, means on each louver at the ends thereof whereby it may be supported, adjacent outer louvers having vertically extending curved side portions defining vertically extending openings therebetween, said curved side portions being curved outwardly of the vent cap, each inner louver in the series being positioned radially inward of one of said openings, each inner louver having a pair of curved concave portions of relatively large radius of curvature joined symmetrically by a convex nose portion of small radius of curvature, the nose portion being located centrally of said opening, each inner louver also having a pair of flanges, one extending from the end of each of said curved portions, each of the flanges being directed radially inward at an angle, the flanges on adjacent inner louvers defining vertically extending ports which have their narrowest dimensions between the radially outer ends of said flanges on adjacent inner louvers, each curved portion of each inner louver cooperating with a side portion of one of the outer louvers to define a passageway between one of the openings and one of said ports, the inner and outer louvers being shaped so that each of said passageways is narrower near the opening than near the port, whereby upon subjecting the vent cap to an external air flow the air passes inward through the openings on the upstream side of the vent cap and flows between the inner and outer series of louvers and out through openings on the downstream side of the vent cap.

4. A series of inner and outer louvers for use in constructing vent caps of a plurality of different sizes, comprising in combination: a circular series of vertically extending inner louvers and a circular series of vertically extending convex outer louvers, the outer series and the inner series having the same number of louvers, means on each louver at the ends thereof whereby it may be supported, adjacent outer louvers having vertically extending curved side portions defining vertically extending openings therebetween, said curved side portions being curved outwardly of the vent cap, each inner louver being positioned radially inward of one of the openings, each inner louver having a pair of curved concave portions of relatively large radius of curvature joined symmetrically by a convex nose portion of small radius of curvature, the nose portion being located centrally of said opening, each inner louver also having a pair of flanges, one extending radially inward from the end of said curved portions, each curved portion of each inner louver cooperating with a side portion of one of the outer louvers to define a passageway between one of the openings and one of said ports, the shape of the inner and outer louvers being such that the number of louvers in each series may be varied to construct vent caps of different sizes while maintaining the width of the openings, the width of the passageways and the width of the ports substantially constant.

5. An inner louver for a vent cap, having a pair of curved concave portions of relatively large radius oi": curvature joined symmetrically by a convex nose portion of small radius of curvature, the louver also having a pair of flanges, one extending at an acute angle from the end of each of said curved portions, the flanges extending at an angle such that when the louver is arranged on a circle in a series with other identical louvers with the nose portions extending radially outwardly that the flanges on adjacent inner louvers define ports therebetween which have their narrowest dimensions between the radially outer ends of said flanges.

References Cited in the file of this patent UNITED STATES PATENTS 2,269,428 Breidert Ian. 13, 1942 2,295,669 Laws Sept. 15, 1942 2,428,544 Breidert Oct. 7, 1947 2,428,545 Breidert Oct. 7, 1947 FOREIGN PATENTS 3,062 Great Britain Mar. 9, 1885 567,526 Great Britain Feb. 19, 1945 91,799 Switzerland Nov. 16, 1921 

